Malachi 1 emphasizes the greatness and love of God. Then, despite how good He has been to the Israelites, they still brought Him their leftovers. They hadn't given God the respect, honor, glory, and worship He deserved. It was the priests' job to determine which animals were acceptable, but instead they were offering blind, lame and sick animals for the sacrifices and keeping the best for themselves. They thought no one would notice them. But God noticed them. And God still notices.
In the state prison system, all the important legal work is dependent on the governor of the state. The governor has the authority to pardon, grant clemency, and shorten our prison sentence. Let's imagine that one day I am asked to prepare a meal for the governor, being on my best behavior. I go to my cell and pick out the cheapest ingredients and put the least amount of effort in cooking the meal, all while keeping the best for myself. Then I present it in a very sloppy way, wearing shabby clothes. Would the governor be pleased? Wouldn't that be super foolish of me? Then why do we treat God that way? In Malachi 1:8 God says, "If you're not going to treat the governor like that, then why do you treat Me like that?"But the good news is that even when we bring God our leftovers, He gives us His best. I am so thankful that even when I am a mess, He washes me clean. I'm so thankful that even when I don't deserve anything, He gives me everything. Even when I am unfaithful, He remains faithful.
In Revelation 3:20, Jesus is walking down the street and sees a familiar house, so He goes to it and knocks and calls out. It is an invitation for dinner. He does the same today. He is still knocking at the doors of our hearts and waiting for us to open it and let Him in so He can eat with us. The question is: Are we going to bring Jesus our best for dinner, or are we going to bring Him our leftovers?